Space & Cosmos

Earth may have had rings 466 million years ago

Regions of equatorial continental crust during the Ordovician Period. Regions older than Ordovician are shown in salmon, Ordovician rocks in dark blue, and newer regions in grey. Light blue indicates lakes in Europe and Russia. Labeled pink dots are recognized as Ordovician impact craters. Credit: Earth and Planetary Science Letters (2024). DOI: 10.1016/j.epsl.2024.118991

In a discovery that calls into question our understanding of Earth’s ancient history, researchers have found evidence suggesting that a ring system on Earth may have formed around 466 million years before the start of an unusually violent period of meteorite bombardment known as the Ordovician impact peak.

This surprising hypothesis, published in Earth and Planetary Science Letters, emerged from a reconstruction of Ordovician plate tectonics that recorded the locations of 21 asteroid impact craters. All of these craters are located within 30 degrees of the equator, an anomaly that cannot be explained by conventional theories, even though more than 70 percent of Earth’s continental crust lies outside this region.

The team believes this localized impact pattern occurred after a large asteroid came close to Earth: as it passed within Earth’s Roche Limit, tidal forces broke it apart, forming a ring of debris around the planet, similar to the rings currently seen around Saturn and other gas giants.

“Over millions of years, material from this ring gradually fell to Earth, causing the largest spike in meteorite impacts seen in the geological record,” said lead study author Professor Andy Tomkins from Monash University’s School of Earth, Atmospheric and Environmental Sciences. “We also know that layers of sedimentary rock from this period contain large amounts of meteorite debris.”

“What makes this discovery even more intriguing is the potential impact such a ring system could have on climate,” he said.

The researchers speculate that the ring could have cast a shadow on Earth, blocking sunlight and contributing to a major global cooling event known as the “Hirnantian Icehouse.”

This period, which occurred near the end of the Ordovician period, is known as one of the coldest periods in the past 500 million years of Earth’s history.

“The idea that the ring system could have influenced Earth’s temperatures adds new complexities to our understanding of how extraterrestrial events have shaped the Earth’s climate,” Prof Tomkins said.

Asteroids usually hit Earth in random locations, which is why we see evenly distributed impact craters on the Moon and Mars, for example. To find out whether the distribution of Ordovician impact craters was not random and closer to the equator, the researchers calculated the surface area of ​​continents that could preserve those craters.

They focused on stable, undisturbed cratons containing rocks older than the Middle Ordovician, excluding areas buried under sediments or ice, eroded areas, and those affected by tectonics. They used a GIS (geographic information system) approach to identify suitable geological regions across different continents.

Areas such as Western Australia, Africa, the North American craton, and parts of Europe were thought to be suitable for preserving such craters. It turns out that only 30% of suitable land masses were located near the equator, yet all impact craters from this period have been found in this region.

The odds of this happening are like flipping a three-sided coin (if such a thing exists) and landing on tails 21 times.

The implications of this discovery go beyond geology, forcing scientists to reconsider the broader influence of celestial events on Earth’s evolutionary history, and raising new questions about the possible existence of other ancient ring systems that may have influenced the development of life on Earth.

Could similar rings have existed at other times in Earth’s history, influencing everything from climate to the distribution of life? This work opens up new areas of study of Earth’s past, providing new insights into Earth’s dynamic interactions with the wider universe.

Further information: Andrew G. Tomkins et al., “Evidence suggesting Earth had rings during the Ordovician,” Earth and Planetary Science Letters (2024). DOI: 10.1016/j.epsl.2024.118991

Provided by Monash University

Citation: Earth may have had a ring system 466 million years ago (September 16, 2024) Retrieved September 16, 2024 from https://phys.org/news/2024-09-earth-million-years.html

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